Temperature-insensitive strain and bright upconversion luminescence in Er-modified 0.88(Bi0.5Na0.5)TiO3-0.22(Bi0.5K0.5)TiO3 ceramics

In this work, 0.88(Bi0.5Na0.5)TiO3-0.22(Bi0.5K0.5)TiO3-xmol%Er (x = 0.00-0.80, 0.88BNT-0.22BKT-xmol%Er) lead-free piezoelectric ceramics were prepared by the solid state reaction method and the effects of Er addition on structure and electrical properties of 0.88BNT-0.22BKT ceramics were investigated. Results showed that Er additive within the content of 0.80mol% diffuse into the 0.88BNT-0.22BKT lattice to form a pure perovskite phase structure. Pure 0.88BNT-0.22BKT ceramic shows a large field strain of 0.21% at room temperature, but it is depended greatly on the temperature. As 0.4-0.8mol%Er doped into the 0.88BNT-0.22BKT host, they show a temperature-insensitive strain characteristic in the temperature range from room temperature to 120 °C. Furthermore, a large electrostrictive effect with high electrostrictive coefficient Q33 of 0.016-0.019m4/C2 comparable with that of traditional lead-based electrostrictors is obtained in these Er-modified materials. Moreover, Er-modified 0.88BNT-0.22BKT samples exhibit a strong green upconversion emission under a 980 nm LD excitation. These results suggest that this kind of material is promising candidate used as multifunctional devices by integrating its electrostrictive and upconversion luminescence properties.